The 20-year-old Bethel Park man who tried to assassinate former President Donald Trump at a Butler County political rally had used “foreign-based encrypted email accounts” and aliases to make more than 25 purchases on firearms websites and buy six “chemical precursors” online since spring 2023, the FBI said Monday.

Authorities said they still don’t know what drove Thomas Matthew Crooks on July 13 to shoot eight rounds at the former president and a crowd of his supporters.

But they stressed that he appeared to be loner whose “careful planning” included canvassing the Butler Farm Show grounds multiple times before the ill-fated rally, where Trump was injured, a local firefighter killed and two others critically wounded.

“We have no information at this time that there are co-conspirators,” Paul Abbate, the FBI’s deputy director, said.

Crooks conducted an online search for “‘How far away was Oswald from Kennedy?’” just days before the shooting, FBI Special Agent in Charge Kevin Rojek from the agency’s Pittsburgh field office told reporters during a briefing for local and national media. The FBI took only a handful of questions.

The would-be assassin also searched online for information about improvised explosive devices, or IEDs; power plants; and the May 16 attempted assassination of Slovakian Prime Minister Robert Fico.

Rojek did not specify what Crooks bought when shopping under aliases at the firearms websites. He also did not identify the vendors or websites. The FBI didn’t immediately respond to emails seeking further comment.

Crooks’ father in 2013 bought the AR-15-style rifle his son used during the shooting, the FBI confirmed. Matthew Crooks “legally transferred” ownership to his son last year.

Authorities also found IEDs in Crooks’ vehicle after the shooting. They didn’t detonate because their receivers were in the “off” position, officials said. A non-functional IED was found in Crooks’ home.

Rojek repeatedly said that his office is working to determine Crooks’ motive and whether he collaborated with others — not scrutinizing any security failings at the Connoquenessing Township event.

More than 300 FBI agents from across the U.S. have been working on the investigation, including roughly half of all field offices and agents from several overseas offices, officials said. More than 450 interviews have been conducted and the FBI currently is working to mine data about Crooks from 86 different companies, according to Rojek.

Secret Service Director Kimberly Cheatle has resigned in the wake of extensive criticism about security failures at the rally. Multiple law enforcement, internal and congressional probes have been announced.

The FBI on Monday added more detail to the emerging portrait of Crooks as a loner — a young man with only family in his “primary social circle,” Rojek said. Only “a couple of people” identified themselves as friends to Crooks and “most of those contacts were, in fact, dated.”

“To date we have not found anyone who is really close to him in any social circle,” Rojek said.

Rojek declined to comment on whether the FBI’s behavioral analysis unit had determined if Crooks fit the profile of a mass shooter or someone who commits political violence.

The FBI has uncovered “no information or evidence of mental health treatment, institutionalization, medication or anything like that,” Rojek added.

Rojek also confirmed the FBI plans to conduct a standard “victim interview” with Trump, which he described as “consistent with any other victim interview we do.”

The Monday morning FBI briefing came hours after the Beaver County SWAT team became the first law-enforcement agency who served on the ground at the Butler County fairgrounds to speak publicly about security failures.

A sniper with the group told ABC News on Monday that the SWAT team had no contact before the shooting with Trump’s security detail. He also said he notified command staff about Crooks when the young man was spotted acting suspicious at the rally about an hour before shots were fired.

The FBI confirmed some of those details in its Monday briefing, including that SWAT members saw Crooks using a range finder around 5:30 p.m.

Crooks visited the fairgrounds before the July 13 rally, as well as the nearby AGR International building from which he shot at Trump, multiple times before the rally, Rojek said.

The day before the rally, Crooks practiced shooting — on the same rifle he later used to shoot at Trump — at a Pittsburgh-area range, officials said.

On the day of the shooting, authorities believe Crooks arrived at the site of the rally around 11 a.m., nearly seven hours before Trump was scheduled to speak. He returned to his Bethel Park home and left again at 1:30 p.m., telling his parents he was headed to a shooting range, the FBI said.

At some point on the day of the attempted assassination, Crooks bought a ladder from an area hardware store but did not use it during the shooting, Rojek said. He instead climbed on HVAC equipment to get onto the AGR building roof.

Officials confirmed a bike and backpack found at the rally didn’t belong to Crooks.

Shortly before 4 p.m., Crooks flew a drone about 200 yards from the rally site for about 11 minutes, Rojek said. Authorities have not found any photos or videos from the drone; there was no memory card in the drone when it was found.

On Thursday, a man who answered the door at Crooks’ home refused to comment. On Monday, Crooks’ family didn’t respond to a phone call seeking comment.

This story is published as part of a collaboration with TribLive.